Like everyone else has said, the tpms could have been damaged in the mounting process. However, look in your owner's manual under tpms or tire pressures, it should tell you in there if you can reset the sensor yourself. Other wise Discount tire should have the nessecary equipment to reset the senors for you (at least mine does anyway).
BTW: the only real way to find out if the tpms was damaged in the mounting process is to have the tire dismounted, by someone who knows what they are doing of course, and visually inspected. If it turns out it was damaged, have the store you bought the tires and had them mounted at buy you a new one (they are pricy!! about $250).